An adapter is used in conjunction with a testing device to test pacing thresholds of an implanted lead. A main body of the adapter includes a plurality of adapter contacts that are configured to electrically couple to the plurality of connector contacts. A connector module includes a first port configured to couple to a first testing device connector and a second port configured to couple to a second testing device connector. A switch assembly includes a plurality of actuatable elements each associated with one of the adapter contacts. The actuatable elements are each selectably actuatable between a first state that electrically couples the associated adapter contact to the first port, a second state that electrically couples the associated adapter contact to the second port, and a third state that electrically decouples the associated adapter contact from the first and second ports.